1. Field of the Invention
The present invention relates to a semiconductor integrated circuit device, and more particularly to a semiconductor integrated circuit device including a non-volatile semiconductor memory in which data are rewritable.
2. Description of the Related Art
A non-volatile semiconductor memory in which data are rewritable, e.g., a NAND type flash memory has a tendency that its storage capacity is further increasing.
With the advancement of miniaturization of a memory cell with an increase in storage capacity, there has emerged a phenomenon which has conventionally rarely appeared, e.g., a phenomenon such as a fluctuation in threshold value due to potentials of floating gates of cells adjacent to each other. This fluctuation in threshold value is called the proximity effect.
The proximity effect fluctuates a threshold value of a memory cell in which data has been already written. This becomes a problem when narrowing a threshold distribution width.
The present invention provides a semiconductor integrated circuit device having a non-volatile semiconductor memory which can realize a narrow threshold distribution width.